The introduction of GPT created the issue that the traditional BIOS can not boot from GPT formatted drives. Newer operating systems can read, initialize, and format drives so that the GPT format can be used on storage drives, but they just can't boot from GPT formatted drives using the old BIOS. The exception is on UEFI motherboards. UEFI replaces the PC BIOS so systems can boot from GPT formatted drives. But there is much more to UEFI than just allowing boot support from GPT drives.

The MBR can only hold enough information to define partitions on drives less than 2.2TB in size. This is where GPT steps in. GPT is becoming an option out of necessity because of the MBR size limitations. With todays drives of 2, 3, and 4TB we need the GPT partition format option in order to utilize all the available disk space on these huge drives. Basically; GPT reserves a portion of the hard drive, in addition to the part reserved for the MBR. GPT uses this reserved disk space to store even more information about the hard drive and its partitions, allowing for hard drive sizes up to 9.4 ZB (zettabytes).

At a slightly more generic level, the BIOS was still a 16-bit real mode program, and thus it was generally so slow and clunky that the OS would bypass it as much as possible. The UEFI is also a bit less heavy. It initializes the hardware and generally just gets out of the way, handing things over to the bootloader.

UEFI was an idea that really came too late. At the time it was considered it would have been revolutionary but they waited too long to implement .Consumers want something they can plug in and it works and they don't care about tweaking settings . The BIOS that exist now on a pc are adequate for the majority of users since a lot of the features of UEFI are now in a lot of the BIOS. By the time UEFI is common it wouldn't surprise me if people that really care about it are over 1% of users.

At a slightly more generic level, the BIOS was still a 16-bit real mode program, and thus it was generally so slow and clunky that the OS would bypass it as much as possible. The UEFI is also a bit less heavy. It initializes the hardware and generally just gets out of the way, handing things over to the bootloader.

OS haven't used the BIOS beyond booting in a very long time. Even XP doesn't rely on the BIOS beyond booting. UEFI is too little too late.